Optical projection: a treatise on the use of the lantern in exhibition and scientific demonstration (1906)

Page scan 000240 from Optical projection: a treatise on the use of the lantern in exhibition and scientific demonstration

Record Details:

Title:
Optical projection: a treatise on the use of the lantern in exhibition and scientific demonstration
Date:
1906
Author:
Wright, Lewis, 1838-1905
Publisher:
London, New York, Bombay : Longmans, Green and Co.
Volume:
Optical projection: a treatise on the use of the lantern in exhibition and scientific demonstration
Leaf #:
000240
Language:
English
Collection:
Books
Format:
Books
Contributor:
University of California Libraries
Sponsor:
MSN
Coordinator:
Media History Digital Library
Date Added:
July 19, 2022
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DEMONSTRATIONS IN PHYSICS 225 best shown by projecting flat soap-films in circular rings, 1 the arrangement of the apparatus being shown in detail at p. 827, where the bands of colour are being projected. At present, however, we are not dealing with colour, but simply with the contractile power of the film. Having lifted a film from the saucer, lay across it a loose thread of fine sewing-silk dipped in the solution ; this thread will also be projected, and it will be seen that it may be moved about freely. Prick on either side of the thread with the end of a small screw of blotting- paper, and the tensile force on the other side at once draws the thread into a curve as fig. 114. In the same way a loose closed loop, pricked in the centre, is at once drawn out into FIG. 114 a circle by the tension of the film. If the ring is carefully flattened, and a straight thin wire wetted with the solution laid across it near one edge, it will adhere; and if the film be pricked in the small space between the wire and the edge of the ring, the tension of the film will pull the wire more or less towards the other side. That the contractile force is greater the smaller the bubble, is projected by blowing two bubbles, one of an inch and the other of two inches diameter, at the open ends of a twice-bent tube, furnished with a stop-cock between them, and with two others which allow communication with separate i The rings should be of wire about 1 mm. diameter, and 2 to 8 inches diameter, and should be coated with paraffin, rubbed on them whilst hot, Q